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Solar energy comes from the sun in the form of electromagnetic radiation. This energy generated by the sun exceeds any known form of energy generated by man. The amount of incoming radiation, known as the solar constant (because it is almost invariable), measured by satellite at Earth orbit, is 1370 watts per square meter.

The sun radiates like all other hot bodies. When the sun's radiation reaches the Earth, it contains wavelengths ranging from invisible ultraviolet, which can cause skin sunburn and eye damage (0.2 to 0.38 micrometers), through the visible rainbow colors (0.38 to 0.75 micrometers) and up to invisible infrared, which we sense as heat (0.75 to 2.5 micrometers). Only low levels of ultraviolet and infrared rays reach the Earth's surface since they are ...

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